The invention relates to the field of infrared (IR) inspection of turbine components, such as turbine blades, turbine vanes, and other turbine items of the like and passages and/or cooling channels for liquid or gas flow. More specifically, the invention relates to simultaneously inspecting more than one side of a turbine blade, while providing protection to an IR imager.
Manufacturing a turbine component may involve casting and machining processes, and each of these processes may introduce variables that affect quality of the component. Controlling the quality of the component is important because the quality of the component may affect its performance.
During the casting process, variables such as core misalignment, inclusions, and the like, can introduce casting defects into the blade. Often times, these casting defects may affect the machining process resulting in machining defects, as well. An example of a turbine component may be a thin or flat object that may be referred to as vanes or blades utilized to cause fluid flow or direct fluid.
For example, a gas turbine blade may include features such as cooling channels and holes. Cooling channels are internal features of the blade through which gases may flow. Because of the internal nature of the cooling channels, cooling channels are, often times, formed during the casting process utilizing casting cores. Defects, such as core misalignments may result in incorrectly formed or blocked cooling channels.
The cooling holes allow the gas flowing through the blade to be exhausted out of the blade. The dimension of the cooling holes may be in the range of 10ths of millimeters. Because of the small dimension of the cooling holes, often times, the cooling holes are machined into the blade after the casting process. In order to control the precision of machining the cooling holes, an automated process may be utilized for the physical drilling of the holes, such as computerized numerically controlled (CNC) machine.
Drilling the cooling holes by CNC machine involves the CNC machine determining the exact position of the cooling holes in three-dimensional space accounting for dimensional tolerances. If casting defects, such as core misalignments, affect the dimensions of the blade to the extent that the dimensional tolerances are exceeded, the cooling holes may not be drilled properly.
Recently, inspection methods involving thermal signatures of materials are being utilized, in particular, infrared (IR) detection imaging. An inspection method utilizing IR imaging involves applying a thermal differential to a turbine component. Often times, applying a thermal differential involves delivering a thermal stimulus, such as a gas, at a high temperature to the blade, and then, immediately following the high temperature thermal stimulus, delivering another thermal stimulus, such as the gas, at a cold temperature (i.e., cold, relative to the high temperature thermal stimulus) to the turbine component. Often times, in inspecting a turbine component, hot and cold gases are used as the inspection medium for delivering thermal stimuli. An example of an IR inspection apparatus may be found in co-pending U.S. patent application Ser. No. 10/062,638 titled xe2x80x9cTURBINE COMPONENT INSPECTION SYSTEMxe2x80x9d, contemporaneously filed, and having common inventorship with present application. The application is incorporated herein in its entirety by reference.
In order to generate high quality images from the IR imager, the IR imager views the turbine component when the turbine component is at its optimum temperatures. However, due to the principles of heat transfer, the optimum temperatures may only last for a couple of seconds. Under the prior art, if more than one side of the turbine component is to be viewed, the IR imager is repositioned and the inspection cycle repeated. Repeating the inspection cycle for the same turbine component may introduce variables, such as thermal gradients, that may adversely affect the results of each inspection for the same turbine component. Further, the features of interest on a turbine component may be on various surfaces, and certain features may require viewing from more than one side of the turbine component.
More than one IR imager could be used to simultaneously view more than one side during an inspection; however, multiple IR imagers would add cost and complexity to the IR inspection apparatus.